Lifetime changes in aspartate carbamyltransferase of reproductive tissue of male rats.

Aspartate carbamyltransferase (ACTase) of the testis, epididymis, and prostate gland was determined throughout the lifetime of rats. Testicular ACTase concentration (nmoles carbamyl aspartate formed per microgram protein) peaked at about 45 g body weight, then declined. Epididymal concentration increased up to 100 g body weight and around 155 g plateaued in the caput and declined slightly in the cauda. A lifetime decline followed the maximal prostatic concentration found in the youngest test rats. Maximal total testicular activity, which occurred at 350 g, was undiminished in the oldest rats, while maximal epididymal activity occurred in the latter group. Total prostatic activity peaked at about 450 g body weight. Castration and testosterone replacement showed prostatic ACTase levels to be hormone dependent.